1. Field of the Invention
The present invention relates to a vehicle lighting device a headlamp or the like using a semiconductor light emitting element (hereinafter referred to as an LED) as a light source and having a heat radiation structure.
2. Background Art
As an example of a conventional vehicle lighting device Patent Document 1 discloses a vehicle lighting device provided with a ventilating path formed inside an outer housing and an air blowing fan in the ventilating path.
As illustrated in FIG. 4, the vehicle lighting device 70 disclosed in the Patent Document 1 is configured to attach each outer lens heating portion 72 to each LED 71 serving as a light source so that heat is transferred to each outer lens heating portion 72 from an associated one of the LEDs 71. Further, a ventilating path 75 is provided inside an outer housing 74 to which an outer lens 73 is fixed. Thus, the outer lens heating portion 72 is placed in the ventilating path 75 in the vicinity of the outer lens 73. Consequently, heat which is transferred to the outer lens heating portion 72 and is generated when the LEDs 71 emit light, is radiated by an air blowing fan 76 disposed in the ventilating path 75.
Moreover, Patent Document 2 discloses another example of a conventional vehicle lighting device which is provided with a housing having a cooling unit, and with an LED attached to a moving plate.
Furthermore, as illustrated in FIG. 5, the vehicle lighting device 80 disclosed in the Patent Document 2 is configured to perform a directional control by attaching an LED 81 to a moving plate 82 . The vehicle lighting device 80 is configured so that a stationary heat radiator 84 provided in a housing 83 is disposed in the vicinity of a cold place of an automobile, that a moving radiator 85 is attached to the vicinity of the LED 81 , and that a convective flow is forcibly generated between the stationary heat radiator 84 and the moving heat radiator 85 by a convective flow generating means 86.
[Patent Document 1] JP-A-2006-294263
[Patent Document 2] JP-A-2006-332052
However, the vehicle lighting device 70 disclosed in the Patent Document 1 is configured so that heat radiated by the LED 71 , the luminous efficiency of which decreases at high temperature, is cooled by the outer lens heating portion 72 in the ventilating path 75 located distant from the LED 71 . Thus, it is difficult to improve heat radiation performance.
In addition, because only the temperature of the outer lens heating portion 72 cooled in the ventilating path 75 is given to the outer lens 73 , it is difficult to improve the snow melting performance of the outer lens 73.
On the other hand, the vehicle lighting device 80 disclosed by the Patent Document 2 is configured so that the convective flow generating means 86 introduces outside air into the housing 83, dust or the like mixed in the outside air is introduced thereinto. Thus, there is a fear of degradation in the luminance characteristics of the lamp.